Adult female rheusus monkeys will be fed a commercial muxture of PBB (Firemaster FF-1) at concentrations of 300 ppm, 30 ppm and 3.0 ppm in the diet. The 300 ppm group will be given the diet for 8 weeks and subsequently switched to a diet containing 0.3 and the 30 ppm group will be on this diet for 3 months and then switched to a 0.3 ppm diet. The 3.0 group will remain on this diet for 1 year and will then be switched to a diet containing 0.3 ppm PBB. The animals will be bred after 6 months on epxeriment. The effects of PBB on fetal and neonatal development will be determined. In vitro metabolism of selected congeners of PBB (2,2',5,5'-HBB, 2,2', 4,5,5'-PBB and 2,2',4,4'5,5'-HBB) will be conducted utilizing rat liver microsomes and the proper generating system. The resulting metabolites will be characterized by means of gas chromatography/mass spectral analysis. The above PBB congeners will also be tested for their toxicity, mutagenicity and transforming ability utilizing in vitro procedures.